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Comment by lostdog | Hacker News Reader

> Doesn't address other major C++ ecosystem problems like build times, packaging, build systems, etc. cpp2 could make them slightly worse.

I assume that as long as the cpp2 syntax is clean, you could improve on compile times. In theory, cpp2 files could compile much more quickly that C++, so as you migrate code to cpp2 your builds speed up?

It all depends on how well Sutter has thought through the cpp2 language design I suppose.

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I said that because the user surveys conducted by ISO clearly identify dependency management and build times as the biggest pain points for C++ engineers. Every proposal doesn't have to work on those problems, but other than parsing (i.e., language designer tech) tooling seems like an afterthought in this case. Just like all of the big ideas coming from ISO leadership.

Big reasons people look for non-C++ solutions include better build times, dependency management, etc.

Modules are a huge benefit for compile times

I've heard discussions that C++ modules didn't really give that much performance benefits as it initially claimed, when the dependency graph is huge and you have a large number of threads. Some links:

- https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p14...

- https://vector-of-bool.github.io/2019/01/27/modules-doa.html

Are there any notable new updates related to this controversy?

Yes, Herb mentions on his talk, import std on VC++ is faster than only doing #include<iostream>, the module version brings the complete standard library.

But it's adding an extra compilation step. The only way to will improve compile times is if it avoids the need to recompile all source files referring to header that's only been modified to add/remove/modify private methods/data in a class (even data is an issue if objects of that class are instantiated on the stack). In principle it might be possible for an extra transpilation step to help there if you also take over the "make"-style dependency management. I'm guessing c++ modules is supposed to help address this too?

The idea is not adding a compilation step. This is a proof of concept and playground. If it works out it's not going to stay as a transpiler to Cpp1 forever

Sure but unless you exclusively use the new syntax (which should be slightly faster to parse, though I'm not sure what % of total compilation time that constitutes) it's still going to have to do at least the same amount of work, if not more (given there's now more that has to be inferred by the compiler, rather than specified explicitly). But from experience the main issue with c++ compliation time is when modifying header files.

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